1. Field of the Invention
This invention relates generally to earthboring tools for boring a hole.
2. Description of the Related Art
Earthboring tools are commonly used to bore holes by cutting through earthen annulus. Such holes may be bored for many different reasons, such as drilling for oil, minerals and water. One type of earthboring tool used for boring is a rotary earth bit. Several examples of rotary earth bits are disclosed in U.S. Pat. Nos. 3,550,972, 3,847,235, 4,136,748, 4,427,307, 4,688,651, 4,741,471 and 6,513,607. A rotary earth bit generally includes an earth bit body comprised of three lugs. A cutting cone is rotatably mounted to each lug with a journal. The journal generally includes ball and roller bearings which engage the cutting cone. The lug rotates in response to the rotation of the earth bit. The cutting cones are engaged with the roller and ball bearings and rotate about the journal in response to contacting earthen annulus.
It is known that earthboring tools wear down with use. For example, the portion of the earth bit proximate to the interface between the lug and cutting cone experiences a significant amount of wear and will cause early failure if it wears too much. Replacing an earth bit is costly and time consuming, so it is desirable to decrease the amount of wear the earth bit experiences.